1. Field of the Invention
The invention relates to a high-pressure fuel pump for an injection system of an internal combustion engine, having a pump housing, having at least one pump element, and having a camshaft for driving the pump element.
2. Description of the Prior Art
One high-pressure fuel pump of the type with which this invention is concerned, known for instance from European Patent Disclosure EP 0 481 964 B2, requires a prefeed pump, which pumps fuel from a fuel tank to the pump element of the high-pressure fuel pump.
The object of the present invention is to furnish a high-pressure fuel pump with an integrated prefeed pump that is constructed simply and can be produced economically. In a high-pressure fuel pump for an injection system of an internal combustion engine, having a pump housing, having at least one pump element, and having a camshaft for driving the pump element, this object is attained in that the pump housing, the camshaft, and a blocking vane cooperating with the camshaft form a blocking-vane pump, and that the blocking-vane pump pumps fuel to the at least one pump element.
By means of this prefeed pump integrated with the high-pressure fuel pump, an otherwise required electrical prefeed pump can be dispensed with entirely or at least for the most part. By the use of components that are present anyway, such as the pump housing and the camshaft, the costs for the blocking-vane pump of the invention are quite low. Moreover, the number of components required is increased only by one blocking vane, so that assembly is not made significantly more expensive, either. Finally, it should be noted that the blocking-vane pump of the invention requires no additional installation space, space that is available to only a very limited extent in modern internal combustion engines and modern vehicles.
In a variant of the invention, it is provided that an inside chamber is recessed out of the pump housing; that the camshaft rotates in the inside chamber; and that the blocking vane and the camshaft divide the inside chamber into a suction chamber and a pressure chamber, so that a blocking-vane pump can be realized at the least possible engineering effort or expense.
In a supplement to the invention, it is provided that a first hydraulic connection exists between the pressure chamber and the pump element, through which the blocking-vane pump pumps fuel to the pump element.
In an especially simple embodiment of the blocking-vane pump of the invention, a groove is provided on the side of the blocking vane toward the pressure chamber, which groove is part of the first hydraulic connection. As a result, the first hydraulic connection can be realized at the least possible effort or expense.
In a further feature of the invention, the pressure chamber is located opposite the pump element, so that at least a partial radial force compensation is created for the camshaft, and moreover the volume of the suction chamber is independent of the position of the piston of the pump element.
It has proved advantageous if a roller tappet is disposed between the pump element and the camshaft, since in this way major forces can be transmitted from the camshaft to the pump element.
Alternative features of the invention provide that the roller tappet is guided in the pump housing; and that a second hydraulic connection is provided between the side of the roller tappet remote from the inside chamber and the suction chamber, so that a pressure equalization is possible. The side of the roller tappet remote from the inside chamber can also be subjected to the pressure of the first hydraulic connection, so that the roller tappet is pressed by the hydraulic force acting on it against the camshaft. In this exemplary embodiment, a spring between the pump housing and the roller tappet can be dispensed with.
To enable better adaptation of the pressing force of the roller tappet on the camshaft, a throttle can be provided in the second hydraulic connection.
The pumping quantity regulation in the high-pressure fuel pump of the invention can be effected by means of an intake throttle regulator or by diverting the excess pumping quantity during the pumping stroke of the at least one pump element, so that the most favorable pumping quantity regulation for a given application can be employed in each case.
Other features of the invention provide that the camshaft has a plurality of cams distributed over its circumference, and/or is embodied integrally with a shaft of the engine, in particular with a compensation shaft or a camshaft, and/or that the high-pressure fuel pump is flanged to the engine, so that the pumping quantity of the high-pressure fuel pump of the invention can be varied within limits by means of the design of the camshaft, and the engineering effort and expense and the installation space required can both be reduced still further.
The high-pressure fuel pump of the invention can be used in particular in a fuel injection system with a high-pressure fuel reservoir (common rail).